Thesis (MSc) -- University of Stellenbosch, 2004. / ENGLISH ABSTRACT: This thesis focuses on the effects of vegetation resting on biodiversity and community dynamics at Rocherpan Nature Reserve (320 36'S, 180 18'E) in the semi-arid coastal strip of the Succulent Karoo known as Strandveld. As a whole, the Succulent Karoo has an extraordinary high level of phyto diversity with high levels of endemism. This is particularly true for succulent shrubs belonging to the groups Mesembryanthemaceae, Crassulaceae and Asteraceae. The thesis begins with an investigation into effects that vegetation resting has on plant diversity. The aim was to determine if resting affected biodiversity levels and if so, which plant groups are affected and why. Through a numerical approach, it was determined that with resting overall species richness remained the same. However, different plant life forms responded to resting differently. With increased resting, abundance of succulent shrubs decreased, while richness of annuals increased. The second aspect under investigation was to determine how resting the vegetation affected community dynamics. The aim was to understand how vegetation structure and interspecific associations changed with resting and to apply these findings to known community models. Through an autocorrelation approach, it was found that horizontal patterning of long-lived woody species, that formed distinctive vegetation clumps, did not change with resting, while differences were found in woody matrix species and succulent species. These changes in structure were investigated further through a study on the demography of specific species. Demography of woody species associated with vegetation clumps did not change with vegetation resting, while significant changes were observed for woody matrix species and succulent species. In longer rested vegetation, woody matrix species showed a greater range in size class distribution (i.e. had both very large and smaller plants) with the tendency towards larger plant sizes. Succulents on the other hand, had a smaller range in size class distribution with a tendency towards larger plants. For all species investigated there were low seedlings counts. It was concluded that succulent shrub populations were 'mature' and continued resting could result in local extinction of some species due to the lack of regeneration. The overall lack of seedlings was attributed to a saturated establishment environment. Implications for conservation management were discussed. / AFRIKAANSE OPSOMMING: Hierdie tesis fokus op die gevolge van plantegroeirus op biodiversiteit en gemeenskapsdinamika by die Roeherpan Natuurreservaat (320 36'S, 180 18"0) in die halfdor kusstrook van die Sukkulente Karoo, bekend as die Sandveld. In die geheel gesien het die Sukkulente Karoo 'n buitengewone hoë vlak plantdiversiteit met hoë vlakke endemie. Dit is veral waar vir sukkulente struike wat tot die groepe Mesembryanthemaceae, Crassulaceae en Asteraceae behoort. Hierdie tesis ondersoek eerstens die gevolge wat plantegroeirus op plantdiversiteit het. Die doel was om te bepaal of rus die biodiversiteitsvlakke beïnvloed het en indien wel, watter plantgroepe en waarom. Deur middel van 'n numeriese benadering is bepaal dat die algehele diversiteit, numeries gesproke, met plantegroeirus dieselfde gebly het. Verskillende plantlewensvorme het egter verskillend gereageer. Met toenemende rus het die diversiteit van sukkulente struike afgeneem, terwyl die diversiteit van jaarplante verhoog het. Die tweede aspek wat ondersoek is, was om te bepaal hoe die plantegroeirus die dinamika van die omgewingsgemeenskap beïnvloed het. Die doel was om te verstaan hoe die struktuur van die plantegroei en die interspesifieke assosiasies verander het met rus en om dan hierdie bevindinge toe te pas op bekende gemeenskapsmodelle. Deur middel van 'n outokorrelasiebenadering is gevind dat die horisontale patrone van meerjarige houtagtige spesies wat in duidelik-uitkenbare plantegroeigroeperings voorkom, nie met rus verander het nie. Veranderinge is egter wel in die houtagtige matriksspesies en die sukkulente spesies waargeneem. Hierdie veranderinge in struktuur is verder ondersoek deur 'n studie te maak van die demografie van spesifieke spesies. Daar is gevind dat die demografie van houtagtige spesies geassosieer met plantegroeigroeperings nie met plantegroeirus verander het nie, maar beduidende veranderinge is waargeneem in die geval van houtagtige matriksspesies en sukkulente spesies. By plantegroei wat langer gerus het, het die houtagtige matriksspesies 'n wyer verspreiding in klasgroottes vertoon (d.i. daar was baie groot plante én kleiner plante) met 'n gemiddelde afname in plantgrootte. Sukkulente, aan die ander kant, het 'n kleiner verspreiding in klasgroottes vertoon met 'n neiging tot groter plante. Vir al die spesies wat ondersoek is, was daar lae saailingtellings. As gevolg van die "volwassenheid" van die populasies van sukkulente struike, sou voortdurende rus, weens die gebrek aan regenerasie, kon lei tot die plaaslike uitwissing van sommige spesies. Die algemene gebrek aan saailinge is toegeskryf aan die versadigde vestigingsomgewing. Die implikasies VIr natuurbewaringsbestuur word bespreek. v

Strandveld vegetation around the Groen river mouth was sampled using complementary ordination and classification techniques (DCA and TWINSP AN). Four communities can be recognised, although samples are primarily divided into inland and coastal plots. Two inland communities are: Stoebaria utilis-Salvia lanceolata community, characterised by tall vegetation(> 1m), on deep, loose soils; Hermannia spp-Leserlia diffusa community of short (<0.6m) vegetation on shallow soils with a hardpan dorbank layer. Two coastal Strandveld communities are: Vanzylia amulata-Limonium peregrinum community which has short vegetation ( <0.5m) on characteristic shallow soils with a calcrete layer at 50 cm deep; Ruschia hutchensonia-Sasola nolothensis community characterised by deep alkaline soils. Of the environmental variables sampled, soil resistance and the presence of calcium carbonate in the soil best explain the distribution of plots and species in ordination space. Communities classified in this study differ subtly from the Tall, Medium and Short Strandveld communities and Strand communities proposed by le Roux and Boucher, 1989 and 1993.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This research considered the automated remote sensing-based classification of wetland extent within the Nuwejaars and Heuningnes River systems on the Agulhas Plain. The classification process was based on meaningful image objects created through image segmentation rather than on single pixels. An expert system classifier was compared to a nearest-neighbour supervised classifier, and one multispectral (SPOT 5) image (dry season) and two C-band, VV-polarisation synthetic aperture radar (SAR: ERS-2) images (dry and wet season) were used separately and in combination. Classifications were performed within two subset areas. Final classes identified were Permanent waterbody, Other wetland and Non-wetland. Statistical accuracy assessment was performed. Validation data was derived from a combination of high-resolution aerial photographs, the SPOT 5 image, high-resolution imagery on Google Earth and observations during a field visit. Wetland extent was defined as the total extent of wetland-specific vegetation, unvegetated seasonal pans and waterbodies. More detailed classes were originally envisaged, but available validation data was not considered adequate for assessing their accuracy with any confidence. The supervised classifier was found to be more accurate overall than the developed expert system. The difference between the two was however not always significant. The two SAR images alone did not contain sufficient information for the accurate classification of Agulhas wetlands’ extent, with recorded overall accuracies not exceeding 65% regardless of the classifier used. The SPOT image alone achieved accuracies higher than 80%; this was considered a good result. In comparison, combining the SAR and SPOT data did not improve the classification accuracy. The potential of the expert system to be applied with little modification to images acquired over other areas or over the same area in other years should be further investigated. However, several reservations are noted in this regard. Future research could potentially improve the results obtained from supervised classification by augmenting it with expert system rules to identify more complicated classes. KEYWORDS ERS-2, SPOT 5, SAR, wetlands, expert system classifier, nearest-neighbour supervised classifier / AFRIKAANSE OPSOMMING: Hierdie navorsing het die geoutomatiseerde afstandswaarneminggebaseerde klassifikasie van vleilandomvang binne die Nuwejaars- en Heuningnesrivier stelsels op die Agulhasvlakte ondersoek. Die klassifikasieproses was gebaseer op betekenisvolle beeldobjekte geskep deur middel van beeldsegmentasie eerder as op enkele beeldelemente. ‘n Deskundige stelsel klassifiseerder is vergelyk met ‘n naaste-naburige gerigte klassifiseerder. Een multispektrale (SPOT 5) beeld vir die droë seisoen, sowel as twee C-band, VV-polarisasie sintetiese diafragma radar (SAR, ERS2) beelde (vir die droë en nat seisoene) is afsonderlik en in kombinasie gebruik. Klassifikasies is uitgevoer binne twee sub-areas in die beelde. Finale klasse wat geïdentifiseer is was Permanente waterliggaam, Ander vleiland en Nie-vleiland. Statistiese akkuraatheidsassessering is uitgevoer. Verwysingsdata is geskep vanuit ‘n kombinasie van hoë- resolusie lugfoto’s, die SPOT 5 beeld, hoë-resolusie beelde op Google Earth en waarnemings tydens ‘n besoek aan die studiegebied. Vleiland omvang is gedefinieer as die totale omvang van vleiland-spesifieke plantegroei, onbegroeide seisoenale panne en waterliggame. Die gerigte klassifiseerder blyk om oor die algemeen meer akkuraat as die ontwikkelde deskundige stelsel te wees. Die verskil was egter nie altyd beduidend nie. Die twee SAR beelde alleen het nie genoegsame inligting bevat vir die akkurate klassifikasie van Agulhas-vleilande se omvang nie, met behaalde algehele akkuraatheidsvlakke wat nie 65% oorskry het nie, ongeag van die klassifiseerder. Die SPOT-beeld alleenlik het algehele akkuraathede van meer as 80% behaal; wat as ‘n goeie resultaat beskou kan word. In vergelyking hiermee kon die kombinering van SAR- en SPOT-data nie ‘n verbetering teweeg bring nie. Die potensiaal van die deskundige stelsel om met min aanpassing op beelde van ander gebiede of van dieselfde gebied in ander jare toegepas te word, verg verdere ondersoek. Verskeie voorbehoude word egter in hierdie verband gemeld. Toekomstige navorsing kan potensieel die resultate van gerigte klassifikasie verbeter deur dit aan te vul met deskundige stelsel reëls vir die klassifikasie van meer komplekse klasse. TREFWOORDE ERS-2, SPOT 5, SAR, vleilande, deskundige stelsel klassifiseerder, naaste-naburige gerigte klassifiseerder.

Thesis (MTech (Applied Sciences))--Cape Peninsula University of Technology, 2007 / Changes in plant specIes richness and diversity were investigated in Rocherpan Nature Reserve across a fence (or old fence line) separating 34 years of conservation management, conservation management for 11 years south and north, natural veld grazed by cattle and goats, natural veld grazed by sheep, and strip-ploughed veld grazed by sheep. Vegetation surveys were conducted in September 2001. The modified 20 m x 50 m Whittaker plot design with its attractive features of long-thin plots and the original Whittaker plot design were used. Number of species (as richness data) and the numbers of individual recordings per species per land use (as abundance data) were used in calculations in the 20 m x 50 m (1000 m2 ) plots. The species richness index showed significantly smaller numbers of species in the conservation management 11 years south land. The results also showed an increase in species numbers under the grazing land use systems. The data from the comparative study of the five different species diversity indices showed no significant differences. As a result, the Shannon-Wiener index was selected for further assessing the species diversity index and the species diversity significance of different land uses in the West Coast Strandveld. In this particular study, the species that showed an increase in vegetation cover in response to grazing land use regimes were Hemimeris racemosa (annual herb) and Ehrharta brevifolia (annual grass).

Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Acacia cyclops, an invasive weed in South Africa, was initially imported to stabilize the sand dunes in the southern Cape. The spread of A. cyclops is a major threat to the fragile biodiversity of the strandveld and limestone fynbos vegetation. Acacia cyclops dieback has been observed for some time, although the causative agent, Pseudolagarobasidium acaciicola, has only recently been described. This fungus is nominated for development as a mycoherbicide to control A. cyclops. Although current biological and mechanical control efforts are proving to be partially effective, A. cyclops is still causing major damage to natural ecosystems. The introduction of a mycoherbicide would increase the cost effectiveness of controlling this weed in the long term. The majority of the literature that was reviewed supports the use of mycoherbicides as biocontrol agents, especially when taking into account the decrease in acceptance and availability of chemical control agents. Considering that the Pseudolagarobasidium genus consists of saprobes, opportunistic facultative pathogens and endophytes, P. acaciicola is predicted to have similar biological characteristics. The species is also highly likely to be indigenous, although with a wider distribution range than previously envisaged. Strict precautions should still however be taken to ensure that non-target species will not be threatened. This study consists of a unique risk assessment comprising different sections. A field survey was performed to record disease incidence among indigenous woody plant species around 100 diseased A. cyclops trees. Subsequently, DNA extractions were made from the roots of the diseased indigenous plants and A. cyclops trees to verify the presence of P. acaciicola. Of the 2432 indigenous woody plants observed, 22 (0.9%) were dead or dying, while P. acaciicola was detected in 10 of these (0.4%), representing six species. Pseudolagarobasidium acaciicola was detected in 47% of the A. cyclops trees. Although P. acaciicola could be a weak pathogen in a broad range of indigenous plant species, the extremely low disease incidence is an indication of a low level of risk associated with using P. acaciicola as a mycoherbicide. Additionally, pathogenicity trials on indigenous plant species were conducted to give an indication of host susceptibility. A total of 30 indigenous plant species were wound inoculated at two field sites, and potted plants representing 17 indigenous plant species were wound and soil inoculated in a nursery. The optimum growth temperature for P. acaciicola was determined in order to understand it’s seasonal and landscape preference. Mortality was recorded in five of nine indigenous Fabaceae species, while a single plant each of four other non-Fabaceae species died after inoculation. No plants outside the Fabaceae family died in the field. Only A. cyclops seedlings died following soil inoculation. Longitudinal sections of stem inoculated plants revealed no systemic infection in Fabaceae species that survived inoculation. Infection in susceptible Fabaceae species was generally more extensive than infection in susceptible non-Fabaceae species. The optimum growth rate for P. acaciicola was determined at 35°C, indicating an adaptation to summer conditions. Indigenous Fabaceae species do display greater susceptibility than species from other families, indicating some level of specificity, although susceptible species can not be phylogenetically circumscribed. Aside from being a facultative pathogen on A. cyclops, results from this study suggest that P. acaciicola is primarily a saprophyte and an occasional opportunistic pathogen on some indigenous Fabaceae, possibly only being a weak opportunistic pathogen on some non-Fabaceae species. However, the risk of not effectively managing A. cyclops populations in these threatened vegetation types outweighs the risk associated with using P. acaciicola as a mycoherbicide. Therefore the use of P. acaciicola as a mycoherbicide on A. cyclops would be recommended, provided that sufficient monitoring of treated sites is implemented that primarily focus on the indigenous Fabaceae species. The effective control of A. cyclops could be achieved when P. acaciicola is used to compliment current mechanical, biological and chemical control methods in an integrated management strategy. / AFRIKAANSE OPSOMMING: Acacia cyclops, ook bekend as rooikrans, is ‘n indringerplant in Suid-Afrika wat oorspronklik vanaf Australië ingevoer is om die sandduine in die Kaap te stabiliseer. Die verspreiding van rooikrans bedreig die sensitiewe biodiversiteit van die strandveld en kalksteen fynbos. Rooikrans terugsterwing is al vir ‘n geruime tyd opvallend in die grootste deel van die plant se verspreiding in Suid-Afrika, alhoewel die veroorsakende organisme, Pseudolagarobasidium acaciicola, eers onlangs beskryf is. Hierdie swam is as ‘n geskikte kandidaat vir die ontwikkeling van ‘n biologiese onkruiddoder om rooikrans te beheer, genomineer. Alhoewel die huidige biologiese- en meganiese beheer metodes vir rooikrans gedeeltelik suksesvol is, hou dié indringer steeds ‘n ernstige bedreiging vir die natuurlike ekosisteme in. Die gebruik van ‘n swam-gebaseerde onkruiddoder sal die beheer van rooikrans oor die langtermyn meer koste-effektief maak. Die oorgrote meerderheid van die literatuur wat hersien is, ondersteun die gebruik van swam-gebaseerde onkruiddoders as biologiese beheermiddels, veral as die afname in aanvaarbaarheid en beskikbaarheid van chemiese beheermiddels in ag geneem word. Aangesien die Pseudolagarobasidium genus uit saprofiete, opportunistiese fakultatiewe patogene en endofiete bestaan, word daar voorspel dat P. acaciicola ‘n soortgelyke biologiese karakter sal hê. Dit is hoogs waarskynlik dat hierdie swamspesie inheems is, alhoewel die verspreiding wyer mag wees as wat oorspronklik voorspel is. Streng maatreëls moet egter steeds in plek wees om te verseker dat nie-teiken plantspesies nie bedreig word nie. Hierdie studie bestaan uit ‘n unieke risiko-analise met verkeie onderafdelings. ‘n Veld-opname is uitgevoer om die siekte-voorkoms van die inheemse houtagtige plantspesies rondom ‘n 100 siek rooikrans plante te bepaal. DNA ekstraksies is vervolgens vanuit die wortels van siek inheemse plantspesies en -rooikrans uitgevoer, om uiteindelik die teenwoordigheid van P. acaciicola binne die hout te kon bevestig. Uit ‘n totaal van 2432 inheemse houtagtige plante wat aangeteken is, was 22 (0.9%) siek of dood, terwyl die teenwoordigheid van P. acaciicola in 10 van hierdie plante (0.4%), wat ses spesies teenwoordig, bevestig is. Die teewoordigheid van P. acaciicola is ook in 47% van die rooikrans bevestig. Alhoewel P. acaciicola moontlik ‘n swak opportunistiese patogeen op ‘n verskeidenheid inheemse plantspesies is, dui die lae verhouding van dooie inheemse plante teenoor gesonde plante in die veld op ‘n lae risiko vir die gebruik van P. acaciicola as ‘n biologiese onkruiddoder. Patogenisiteitstoetse is op inheemse plantspesies uitgevoer om ‘n aanduiding van gasheervatbaarheid te verkry. Wond-inokulasies is op ‘n totaal van 30 inheemse plantspesies by twee veldstudie-areas uitgevoer, terwyl wond- en grond-inokulasies op 17 inheemse spesies potplante in die kweekhuis uitgevoer is. Die optimale temperatuur waarby P. acaciicola groei, is bepaal om die swam se seisoenale- en habitatsvoorkeure beter te verstaan. Plante van vyf uit die nege inheemse Fabaceae spesies het doodgegaan, terwyl ‘n enkele plant van vier nie-Fabaceae spesies doodgegaan het. Alle plante buite die Fabaceae familie het oorleef in die veld na inokulasie. Slegs rooikranssaailinge het na grond inokulasie doodgegaan. Lengtedeursnee van die stam en wortels van elke geïnokuleerde plant het bevestig dat daar geen sistemiese infeksie in Fabaceae spesies wat inokulasie oorleef het, plaasgevind het nie. Infeksies in vatbare Fabaceae spesies was oor die algemeen meer ernstig as infeksies in vatbare nie-Fabaceae spesies. Die optimale groei van P. acaciicola het by 35°C plaasgevind, wat aandui op ‘n voorkeur vir somerstoestande. Inheemse Fabaceae spesies het meer vatbaar as vatbare plantspesies van ander families voorgekom. Hierdie verskynsel dui op ‘n sekere vlak van spesifisiteit, alhoewel daar geen duidelike filogenetiese grense vir vatbare spesies bepaal kon word nie. Behalwe vir die feit dat P. acaciicola ‘n fakultatiewe patogeen op rooikrans is, stel resultate van hierdie studie voor dat hierdie swam hoofsaaklik ‘n saprofiet is wat soms ook ‘n opportunisties patogeen op sekere inheemse Fabaceae is en moontlik slegs ‘n swak opportunistiese patogeen op plantspesies buite die Fabaceae familie is. Die swak en oneffektiewe bestuur van rooikrans in hierdie bedreigde plantegroeitipes hou egter ‘n groter bedreiging in as die gebruik van P. acaciicola as ‘n biologiese onkruiddoder. Pseudolagarobasidium acaciicola word daarom aanbeveel vir die beheer van rooikrans, mits voldoende monitering, wat fokus op inheemse Fabaceae spesies, gepaard gaan met die gebruik van hierdie biologiese onkruiddoder. Rooikrans kan effektief beheer word as P. acaciicola ingespan word om huidige meganiese-, biologiese- en chemiese beheermetodes in ‘n geïntegreerde bestuurstrategie te komplimenteer.

Dissertation presented for the degree of Doctor of Philosophy (PhD) at Stellenbosch University. / Thesis (PhD (Conservation Ecology and Entomology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The South African Cape lowlands have been severely transformed and reduced to fragments embedded in matrices of various activities. With the need to prioritise conservation efforts, information on the conservation worthiness and management of these fragments is required. This study aimed to better understand how fragmentation affects the Cape lowland vegetation patterns and dynamics and more specifically, to determine if, and if so to what extent these fragments contribute to regional plant diversity and more importantly their functionality. The novel approach adopted focused on plant functional traits, which are better predictors of ecosystem response to global change than individual species. Species were sampled at four scales in four sites of decreasing sizes, including: a mainland and three fragments of three Cape lowland vegetation types i.e. Atlantis Sand Fynbos (ASF), Swartland Shale Renosterveld (SSR) and Langebaan Dune Strandveld (LDS). Traits such as dispersal, pollination, breeding mode and longevity were selected based on relevance to species’ and plantfunctional types’ (PFTs) responses to fragmentation. The findings revealed different effects on species richness and PFTs. The effect of reduced patch size on species richness was more evident in ASF where fragments below 600 ha had significantly fewer species than the mainland. This effect was not unequivocal in SSR and LDS due to several confounding factors (notably the grazing history of the sites). The SSR fragment grazed by indigenous herbivores had significantly more species than the ungrazed sites. Also, the largest LDS fragment grazed by livestock had significantly more species than the ungrazed mainland, indicating that grazing rather than fragment size influences species richness, although the smallest fragments of these two vegetation types had significantly fewer species than the larger fragments. Species turnover and complementarity were high for all three vegetation types, reflecting the degree of habitat heterogeneity and high contribution of beta diversity to overall gama diversity. The effect of reduced patch size was higher on PFT diversity than on PFT richness, with Langebaan Dune Strandveld where habitat fragmentation was more recent being the least affected of the three vegetation types. This indicates a degree of functional redundancy in the Cape lowlands, which is important for ecosystem resistance and resilience. The ASF mainland and the largest fragment had higher PFT diversity than the medium-sized and the smallest fragments; the mainland had also higher PFT diversity than all the fragments combined. Similarly, the smallest SSR fragment had significantly lower PFT diversity and richness than the other sites. The grazed SSR fragment had higher PFT richness and diversity than the ungrazed mainland and smallest fragment, indicating the role of grazing in maintaining renosterveld vegetation. The PFTs absent from the different sites were mostly short-distance dispersed dioecious and non-dioecious species, and some with highly specialised pollination systems. This suggests that dispersal and pollination are vital functional attributes for the persistence of the studied fragmented ecosystems. Habitat fragmentation effects plant community composition and ecological functions in the Cape lowlands, a conclusion supported also by the revealed significant trait-convergence and divergence assembly patterns. These communities result from various fragmentation filters that operate at different spatial-temporal scales and selecting species with suitable responses. All three vegetation types are susceptible to fragmentation, albeit at varying degree. The fragmentation effect was confounded by the sampling and temporal scales, the nature of disturbance regime, and the traitmediated differences in species’ response. The role of the surrounding matrix on fragment connectivity and gene flow appears to be of crucial importance, hence mitigation measures focusing on improving connectivity between patches, monitoring threatened taxa, and promoting dispersal and pollination have been recommended. / AFRIKAANSE OPSOMMING: Suid-Afrika se Kaapse laagland het dramaties verander en weggekwyn tot fragmente wat in matrikse van verskeie bedrywighede veranker is. Gedagtig aan die voorkeuraandag wat bewaringspogings tans geniet, is inligting oor die bewaringswaardigheid en bestuur van hierdie fragmente nodig. Hierdie studie stel dit ten doel om beter begrip te vorm van hoe fragmentasie die plantegroeipatrone en -dinamiek in die Kaapse laagland raak, en meer bepaald om vas te stel óf, en indien wel, in watter mate, hierdie fragmente tot streeksplantdiversiteit en -funksionaliteit bydra. Die ongewone studiebenadering konsentreer op funksionele kenmerke van plante, wat beter aanwyser van ekosisteemreaksie op wêreldwye verandering is as individuele spesies. Spesiemonsters is op vier skale by vier terreine van wisselende grootte ingesamel, wat insluit moederstrook en drie fragmente van elk van drie plantegroeisoorte in die Kaapse laagland, naamlik Atlantis-sandfynbos (ASF), Swartland-skalierenosterveld (SSR) en Langebaan-duinestrandveld (LDS). Kenmerke soos verspreiding, bestuiwing, voortplantingsmetode en lewensduur is gekies op grond van die tersaaklikheid daarvan vir spesies en plantfunksionele tipes (PFT’s) se reaksie op fragmentasie. Die studie bring verskillende uitwerkings op spesie-oorvloed en PFT’s aan die lig. Wat spesie-oorvloed betref, was die uitwerking van kleiner strookgrootte (“patch size”)duideliker te sien by ASF, waar fragmente kleiner as 600 ha beduidend minder spesies as die moederstrook bevat het. Hierdie uitwerking kon nie so duidelik by SSR en LDS waargeneem word nie weens verskeie strengelingsfaktore, veral die weidingsgeskiedenis van die terreine. Die SSR-fragment waarop inheemse herbivore gewei het, het beduidend meer spesies as die onbeweide terreine bevat. Voorts het die grootste LDS-fragment waarop vee gewei het heelwat meer spesies as die onbeweide moederstrook gehad, wat daarop dui dat weiding eerder as fragmentgrootte spesie-oorvloed beïnvloed, hoewel die kleinste fragmente van hierdie twee plantsoorte steeds aansienlik minder spesies as die groter fragmente bevat het. Spesie-omset en -aanvullendheid was hoog vir ál drie plantsoorte, wat aanwyser is van die mate van habitat-heterogeniteit en die groot bydrae wat betadiversiteit tot algehele gammadiversiteit lewer. Die uitwerking van kleiner strookgrootte was duideliker te bespeur op PFT-diversiteit as PFT-oorvloed – in dié verband het LDS, waar habitatfragmentasie mees onlangs plaasgevind het, die ligste van die drie plantsoorte afgekom. Dít dui op mate van funksionele oorbodigheid in die Kaapse laagland wat belangrik is vir ekosisteemweerstandigheid en -gehardheid. Die ASF-moederstrook en die grootste ASF-fragment het hoër PFT-diversiteit getoon as die medium- en kleinste fragmente; die moederstrook het in werklikheid oor hoër PFT-diversiteit as ál die fragmente saam beskik. Insgelyks het die kleinste SSR-fragment beduidend minder PFT-diversiteit en -oorvloed as die ander terreine getoon. Die beweide SSR-fragment was hoër in PFT-oorvloed én -diversiteit as die onbeweide moederstrook en die kleinste fragment, wat die rol van weiding in die instandhouding van renosterveldplantegroei beklemtoon. Die PFT’s wat nié op die verskillende terreine voorgekom het nie, was meestal tweehuisige en nietweehuisige spesies wat oor kort afstande versprei, en sommige spesies met hoogs gespesialiseerde bestuiwingstelsels. Dít dui daarop dat verspreiding en bestuiwing noodsaaklike funksionele kenmerke vir die voortbestaan van die bestudeerde gefragmenteerde ekosisteme is. Habitatfragmentasie raak die samestelling en ekologiese funksies van plantgemeenskappe in die Kaapse laagland. Dié gevolgtrekking word ook gerugsteun deur die bewese patrone van beduidende kenmerkkonvergensie (“trait convergence”) en divergensiesamekoms (“divergence assembly”). Hierdie plantgemeenskappe spruit uit verskeie fragmentasiefilters wat op verskillende ruimte-tydskale funksioneer, en wat spesies met geskikte reaksies kies. Ál drie plantsoorte is ontvanklik vir fragmentasie, hoewel in wisselende mate. Die fragmentasie-uitwerking is beïnvloed deur monsterinsameling- en tydskale, die soort versteuringsbedeling, en die kenmerkbemiddelde (“traitmediated”) verskille in spesiereaksie. Die rol van die omringende matriks op fragmentverbondenheid en geenvloei blyk van die allergrootste belang te wees, en dus word temperingsmaatreëls aanbeveel wat daarop gemik is om verbondenheid tussen stroke te verbeter, bedreigde taksa te moniteer, en verspreiding en bestuiwing aan te help.

Thesis (MScAgric (Soil Science))--University of Stellenbosch, 2005. / The purpose of this study was to investigate and identify the occurrence of specific soil properties that may be important for vegetation functioning and the possible effect of the loss of or changes in these properties on rehabilitation success on the sandy coastal plains of the West Coast, South Africa. The study area covered approximately 9 400 ha on the Namaqualand coast in the vicinity of Brand-se-Baai (31º18'S 17º54'E), approximately 350 km north of Cape Town and 70 km north-west of the nearest town, Lutzville. A soil survey was done to reveal the presence of important pedological features. The 20 soil profiles surveyed are situated within six vegetation communities. Pedological features such as surface water repellency, permeable apedal subsurface horizons, subsurface impediments such as cemented (calcrete or dorbank) hardpans and significantly more clayey (cutanic, luvic) horizons were identified. A comparative study between rehabilitated and natural soils indicates that mining operations result in the formation of saline sand tailings, stripped of a large portion of the clay and organic matter fraction. The natural leaching of solutes, over a period of 25 months, is sufficient to lower salinity of the tailings to levels comparable to natural soils. This leaching can also results in lowering of soil fertility. Removal of the dorbank and the dense neocutanic horizon in the western side of the mine, loss of topographical features such as small dune systems and heuweltjies, destruction of natural soil profile morphology and the lowering of organic carbon and clay plus silt fraction can have detrimental effects on attempts at rehabilitation of this area to a natural condition similar to that which preceded the mining operation. Infiltration fingering and deep percolation results in the development of an aquifer below the reach of shallow-rooted desert shrubs. A method of water acquisition by vegetation through water distillation is investigated as a possible solution to the apparent discontinuum between the shallow root systems and deeper-lying aquifer. Volumetric water content measurements indicated that precipitation of 29.5 mm, over a period of 10 days, did not result in any variation at 235 mm, 360 mm and 900 mm depths. An average volumetric water content increase of 0.4 mm per night was measured in the first 23.5 cm of soil surface. This amount is a significant source of water that can explain the shallow root distribution. Water vapour movement due to temperature gradients can explain the diurnal volumetric water content fluctuations observed. Further studies are necessary to determine to what extent the depth of water infiltration influences the capacity of subsurface dew to provide plants with a nocturnal water source. Findings of this study can be summarised into two concepts namely: • Heuweltjies, small dune systems, and variation in depth of cemented hardpans are the main features that contribute to pedosphere variation and possibly to biodiversity. • Pedogenic features such as topsoil hydrophobicity, and cemented dorbank and dense more clayey (cutanic, luvic) subsurface horizons are important components of a soil water distillation process that could be a driving force behind vegetation functioning in this region. Mine activities result in the loss of certain pedogenic features and soil properties that that could be key ingredients to ecosystem functioning. The inability to recognise their significance and ignorance thereof when planning rehabilitation methods might prevent sustainable restoration of the environment.

A grazing trial investigating the effect of season of grazing and stocking rate initiated at the Nortier Experimental Farm in 1988 provided an opportunity to assess the response of the veld to both grazing and environmental influences in an arid environment. The trial allowed an assessment of the relative influence of internal (equilibrium) and external (non-equilibrium) forces on the dynamics of an arid rangeland. This study involved the analysis of a nine year data set stretching from 1988 to 1996 and served to provide evidence supporting the existence of an equilibrium/non-equilibrium continuum in rangeland dynamics. The most significant implication of this result is that rangeland systems should not be classified as either equilibrial or non-equilibrial, but rather according to a continuum extending between equilibrium and non-equilibrium poles. The exact position of any system on this continuum is a function of the relative influence of internal and external forces on its species dynamics. The dynamics of the veld at the Nortier Experimental Farm showed significant response to both grazing and environmental variables suggesting conformity to both equilibrial and non-equilibrial paradigms. Both ordination and analysis of variance highlighted the importance of rainfall particularly in the fluctuations of the predominant grass species, Ehrharta calycina, which increased in abundance with rainfall. Partial ordination enabled the assessment of species variation following the removal of variation associated with rainfalL Partial ordinations revealed the gradual, directional movement of samples through multivariate space in response to grazing treatments. Individual plant species were also shown to be responding to grazing, the extent of which was influenced by season of grazing and stocking rate. Both the partial ordinations and the ANOVA showed Melothria sp., Tetragonia fruiticosa and Hermannia scordifolia as increasing and Ruschia caroli as decreasing in absolute abundance in response to grazing. Season of grazing was shown to significantly influence the abundance of H. scordifolia over time. The 'shrublherb complex', which constitutes the 'key resource' at the Nortier Experimental Farm displayed an increase in absolute abundance over the duration of the trial. This increase in absolute abundance was accompanied by an increase in the relative abundance of the palatable component of this resource. The application of medium to heavy stocking rates during spring, summer and autumn and low stocking rates during winter resulted in elevated absolute abundances of palatable plants. Furthermore, low stocking rates, when averaged across all season of grazing treatments, resulted in a significantly higher absolute abundance of unpalatable plants. These findings provide the basis for the development of management principles for the Strandveld Vegetation Type. The application of medium to heavy stocking rates within a rotational grazing system, as recommended by the literature dealing with grazing systems in the Karoo, is supported by the results of the Nortier grazing trial. Medium to heavy stocking rates should be applied during spring, summer and autumn and low stocking rates during the winter months. Furthermore, it is recommended that rests of between 12 and 14 months should be afforded to portions of the veld periodically due to the variability in growth, flowering and fruiting times ofdifferent plants in the Karoo. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.